Electrodeposition of bright tin-nickel



United States Patent 3,141,836 ELECTRODEPQSHTION 0F BRIGHT TIN-NICKELEdgar .ll. Seyb, in, Oak Park, and Augustine J. Wallace,

in, East Detroit, Mich, assignors, by mesne assignments, to M a TChemicals inc, New York, N.Y., a

corporation of Delaware No Drawing. Filed June 17, 1960, Ser. No. 36,75022 Claims. (Cl. 204-43) The present invention is directed to improvedbaths and process for electroplating tin-nickel alloys and to brighttin-nickel electrodeposits.

Plating baths for electrodepositing tin-nickel have excellent throwingpower. Although the electrodeposits obtained from commercial baths arefairly attractive, the deposits are not as clear and bright as requiredfor most decorative applications. Only those deposits plated over abright undercoat in thicknesses less than 6 microns appear bright.Essentially here the deposit is transparent. In thicknesses greater than6 microns, there is a slight white clouding-over of the depositresulting in a hazy deposit, which increases with increased thickness.It is desirable to have a clear, lustrous deposit and even moredesirable to have a clear, bright deposit. We have now discovered aprocess utilizing special baths from which we are able to electrodepositbright tin-nickel.

It is an object of this invention to provide lustrous tin.- nickel alloyelectrodeposits.

It is also an object of this invention to provide bright tin-nickelelectrodeposits in thicknesses greater than 6 microns.

The invention also contemplates improved baths electrodepositinglustrous, clear and bright tin-nickel alloys in thicknesses greater than6 microns.

The invention further contemplates a process for electrodepositinglustrous, clear, and bright tin-nickel electrodeposits in thicknessesgreater than 6 microns.

We discovered that lustrous and bright tin-nickel electrodeposits may beobtained from acidic baths which contain an effective amount of abrightener. We discovered that specific compounds and combinations ofspecific compounds are effective brightene-rs for tin-nickel alloyelectrodeposition.

The electrodeposit may be made on dull basis metals, although this isnot preferred. As deposited initially, the tin-nickel is fairly brightand as electrodeposition continues, the deposit becomes increasinglybright resulting in a lustrous deposit. Tin-nickel as electrodepositedfrom standard baths may be described as cloudy-bright. The deposit has aslight white clouded appearance. It is not lustrous. We have been ableto increase brightness to (i) hazy-bright, a slight background haze inan essentially clear deposit, and (ii) clear-bright, brightnessapproaching that normally associated with a mirror. By using the variousadditives specified hereinafter, it is possible to obtain hazy-brightand/or clear-bright deposits. These deposits are lustrous. Lustrous andbright deposits are obtained from acid baths containing, as abrightener, phenylpropiolic acid; phenylpropiolic amide;triaminotriphenyl methane; l-(p-aminophenyl)-3-methylpyrazole;steanamidopropyldimethyl-(fl hydroxyethyhammoniurn dihydrogen phosphate;or 1,S-diphenyloarbohydrazide.

These bright deposits are physically different from any heretoforeproduced. They apparently have a finer-grained structure. They differappreciably in the grain orientation taining 0.01 g./l. and 0.1 g./l.are used.

with strong layering in the 300 plane. X-ray diffraction data follows:

The designation of the intensity of the lines is as follows:

vsvery strong s-strong Inmedium w-weak vwvery weak The data for thedeposit noted in column A is reproduced from I. of ElectrodepositersTech. Soc., 27, 156 (1950- 51), as is the and hkl values. The data incolumn B is for a deposit obtained from Both No. 2 of Table II herein,using the potassium salt of perfluoroethylcyclohexane sulfonate as ananti-pitting agent. The bright deposits recorded in column C and columnD were from the same bath as that of column B; the bath of column C alsocontaining 0.2 g./l. of phenylpropiolic acid as a brightener; and thatof column D containing 0.2 g./l. of steanamidopropyldimethyl-(,6hydroxyethyDamrnonium d-ihydrogen phosphate as a brightener. Thedeposits of columns B, C, and D were 0.015 cm. thick.

Phenylpropiolic acid, phenylpropiolic amide, and triaminotriphenylmethane are useful brighteners when added to the baths in amountsbetween 0.01 g./l. and 0.3 g./ 1.; preferably baths containing 0.05g./l. and 0.2 g./l. are used. l-(p-aminophenyl)-3-methylpyrazole is auseful brightener when added to the bath in amounts between 0.05 g./l.and l g./l.; preferably baths containing 0.2 g./l. and 0.5 g./l. areused. Stearamidopropyldimethyl- (fi-hydroxyethyl-ammonium dihydrogenphosphate is a useful brightener when added to the bath in amountsbetween 0.001 g./l. and 0.2 vg./l.; preferably baths com1,5-diphenylcarbohydrazide is a useful brightener when added to the bathin amounts between 0.05 g./l. and 0.5 g./l.; preferably baths containing0.2 g./l. and 0.3 g./l. are used.

When one of the aforementioned brighteners is used as the solebrightener in the bath, effective brightening action is not achievedwhen the bath contains less than the minimum concentration specified foreach brightener. Smaller concentrations may be extremely effective whenmore than one brightener is used in combination. The maximum preferredconcentration specified for each brightener is that concentration atwhich acceptable brightness will be achieved with the variation ofconditions to be found in commercial practice. Above the preferredmaximum concentration specified, the deposit tends to become brittle athigh current densities (above about 7.5 amp./ sq. dm.). Above themaximum concentration specified, the brittleness becomes severe enoughto cause cracking and some exfoliation so that the current density rangeis substantially reduced.

Phosphoric acid and its salts have also been discovered to bebrighteners. Phosphoric acid when added to the bath in amounts between0.1 g./l. and 15 g./l., and preferably between 0.5 g./l. and 7 g./l.,results in lustrous, hazybright deposits. The brightness activity ismost significant in the 0.5-7.0 g./l. range. Although amounts in excessof 7.0 g./l. up to 15 g./l. do not appear to produce an increase in thebrightness of the deposit, this presence does not give detrimentaleffects. Above about 15 g./l., the deposit possesses a grainyappearance. Concentrations of less than 0.5 g./l. are effective Whenused in combination with a sufiicient concentration of anotherbrightener. Phosphoric acid as used herein includes the ortho, pyro,metaand hypo-phosphoric acid as well as the equivalent series of salts.The potassium, sodium, and ammonium salts are preferred.

Combinations of the various brighteners give unusually good deposits; inparticular, deposits approaching mirrorbrightness have been obtained byusing phosphoric acid in combination with one of the other brighteners.Although the ranges in which the individual brighteners are effectiveare also the same general ranges in which they are effective incombination, it is possible to use amounts smaller than the minimumspecified concentration of one brightener, in combination with anotherbrightener in relatively higher concentrations. The combinations ofbrighteners are particularly preferred in that the brightest depositsare obtained with combinations of brighteners. The use of phosphoricacid in combination with one of the other brighteners has beenparticularly useful in that it tends to broaden the limits of the rangeof concentrations of brightener permitted in the bath. A preferredmethod of incorporating the brightener in the bath is to add a watersolution containing g./l. to 200 g./l. of phosphoric acid and 5 g./l. to50 g./l. of at least one of the other brighteners specified herein.

Tin-nickel is deposited from acid baths, primarily from chloride and/ orfluoride baths. The preferred baths contain both chloride and fluorideanions; stannous tin in the amounts of 26 g./l. to 37.5 g./l.; andnickel in amounts between 60 g./l. and 82.5 g./l. The total fluorine fornew baths is between 34 g./l. and 45 g./l. in the mixed baths. Thestannic tin concentration increases in baths which are in operation. Asthis occurs, the fluorine should be increased so that it at least equalsthe total tin in the bath. The chloride content is not critical. The pHis maintained between 2 and 3.5, generally by the addition of ammoniumhydroxide or hydrofluoric acid. To prevent pitting, the baths shouldalso contain a suitable agent. A class of agents which has been found tobe satisfactory includes a sulfonated cyclic fluorocarbon such asperfluoro-4-methyl cyclohexyl sulfonic acid; perfluorocyclohexylsulfonic acid; perfluoro-Z-methyl cyclohexyl sulfonic acid;perfluoro-1-rnethyl cyclohexyl sulfonic acid; perfluoro-2,5-dimethylcyclohexyl sulfonic acid; perfluoro-4- ethyl cyclohexyl sulfonic acid;perfluoro-4-isopropyl cyclohexyl sulfonic acid; and the salts of theseacids. The bath is operated at high temperatures, preferably between 65and 71 C. Typical bath formulations follow:

Table II BATH 1 Grams per liter Stannous chloride, SnCl 42 (Tin metal)26 Nickel chloride, NiCl -6H O 300 (Nickel metal) 75 Sodium fluoride,NaF 28 (Fluoride) 13 Ammonium bifluoride, NH HF 35 (Fluorine) 24 Totalfluorine in bath 37 pH (colorimetric), 2.5. Temperature, 65 C. Cathodecurrent density, 3 amp/sq. dm.

Table ill-Continued BATH 2 Grams per liter Stannous chloride 49 Nickelchloride (NiCl -6H O) 300 Ammonium bifiuoride (NH HF 56 Ammoniumhydroxide, as needed to adjust pH to 2.0-2.5. Temperature, 68 C.

All-chloride baths are generally operated at lower pHs, i.e., notgreater than about 1, by the addition of hydrochloric acid. In theseall-chloride baths, the tin is added in the form of stannous chloride,and the nickel in the form of nickel chloride. All of the baths areinitially made up by adding the noted chemicals to water. However,equivalent chemicals may be added, e.g., stannous tin may be added inthe form of the oxide or the fluoride, as well as the chloride. Duringoperation, the tin and nickel may be replaced either chemically or byanodic corrosion of metallic anodes or a combination of both.

For the purpose of giving those skilled in the art a betterunderstanding of the invention, the following illustrative examples aregiven. In the examples, tin-nickel (approximately 65% tin and 35%nickel) was electrodeposited at the conditions noted. The physicalappearance of the deposit obtained in each example is described. Asnoted they are lustrous and bright and in some cases they are aclear-bright.

All the samples were plated from the standard bath identified as Bath 2of Table II hereinbefore. Plating tests were made under two differentsets of conditions as specifically noted in each example. Most of thetest cathodes were plated in a Hull Cell which is described on pages645-648 of The Metal Finishing Guidebook, 27th edition (1959). With thisprocedure, the current density changed along the length of the panel sothat the appearance of a deposit could be examined over a currentdensity range of about 0.5 to 8 amperes per square decimeter. In theother tests, small zinc die cast handles were used. This showed thetin-nickel deposit as it would appear on a production part. When theZinc part was used, the plating was done in a small laboratory tankrather than in a Hull Cell. In both instances, mild solution agitationwas used.

EXAMPLE 1 Triaminotriphenyl methane was added to the standard bath inthe amount of 0.25 g./l. Under the standard plating conditions, a smallcopper plated zinc die cast handle was plated at an average currentdensity of approximately 2.3 amperes per square decimeter (amp/sq. dm.)for 25 minutes to an average thickness of approximately 20 microns. Thedeposit was clear-bright over the decorative area of the handle to givea lustrous, attractive article.

EXAMPLE 2 Triaminotriphenyl methane in the amount of 0.05 g./l. wasadded to the standard bath which was placed in a Hull Cell. In thisplating cell, a smooth brass panel was plated as cathode for 10 minuteswith the current adjusted so that the current density ranged from a lowof approximately 0.0'5 amp/sq. dm. at one end of the panel to about 8amp./ sq. dm. at the other end of the panel. The average thickness ofthe tin-nickel was approximately 9 microns and the thickness at the highcurrent density end of the panel was approximately 27 microns. Thedeposit was hazy-bright in appearance over the entire panel.

EXAMPLE 3 Phenylpropiolic acid in the amount of 0.2 g./l. was added tothe standard bath in a small plating tank. Tinnickel was plated directlyon a steel cathode at an average current density of 2.3 amp/sq. dm. for45 minutes to give an average thickness of approximately 40 microns. Atthis thickness 2. hazy-bright deposit was obtained over the surface ofthe cathode.

EXAMPLE Phenylpropiolic acid in the amount of 0.04 g./l. was added tothe standard bath formulation in a Hull Cell. With a smooth brass panelas cathode plated at 2.7 amp/sq. dm. for minutes, the deposit washazybright.

EXAMPLE 6 Phenylpropiolic amide in the amount of 0.25 g./l. was added tothe standard tin-nickel bath in a Hull Cell. A smooth brass panel wasplated at an average current density of 2.7 amp/sq. dm. for ten minutes.At the end of this time the plate was clear-bright and lustrous over allbut the high current density edge of the current density range.

EXAMPLE 7 Phenylpropiolic amide in the amount of 0.2 g./l. was added tothe standard tin-nickel bath in a small laboratory tank. A copper-platedzinc die cast handle was plated at approximately 2.3 amp./ sq. dm. for30 minutes. An average tin-nickel thickness of approximately 23 micronswas obtained. The deposit was clear-bright and lustrous.

EXAMPLE 8 Phenylpropiolic amide in the amount of 0.1 g./l. was added tothe standard tin-nickel bath formulation in a Hull Cell. A smooth brasspanel was plated for 10 minutes at an average current density of 2.7amp/sq. dm., the deposit obtained was clear-bright over the entirecurrent density range.

EXAMPLE 9 The compound l-(p-aminophenyl)-3-methylpyrazole in the amountof 0.5 g./l. was added to the standard tinnickel formulation in a HullCell. A smooth brass panel was plated at an average current density of2.7 amp./ sq. dm. for 10 minutes. The tin-nickel deposit was clearbrightover the entire panel.

EXAMPLE 10 The compound 1-(p-aminophenyl)-3-methylpyrazole in the amountof 0.1 g./l. was added to the standard tinnickel formulation in a HullCell. A smooth brass panel was plated at an average current density of2.7 amp/sq. dm. for 10 minutes. The tin-nickel deposit was clearbrightover the entire panel.

EXAMPLE 11 The compound,stearamidopropyldimethyl-(/3-hydroxyethyl)-ammonium dihydrogen phosphatein the amount of 0.12 g./1. was added to the standard tin-nickelformulation in a Hull Cell. A smooth brass panel was plated at anaverage current density of 2.7 amp/sq. dm. for 10 minutes. Thetin-nickel deposit was clear-bright over the entire panel.

' EXAMPLE 12 The compound,stearamidopropyldimethyl-(fi-hydroxyethyl)ammonium dihydrogen phosphate,in the amount of 0.04 g./l. was added to the standard tin-nickelformulation in a Hull Cell. A smooth brass panel was plated at anaverage current density of 2.7 amp./ sq. dm. for 10 minutes. Thetin-nickel deposit was clear-bright over the entire panel.

EXAMPLE 13 The compound 1,S-diphenylcarbohydrazide in the amount of 0.4g./l. was added to the standard tin-nickel 0 formulation in a Hull Cell.A smooth brass panel was plated at an average current density of 2.7amp/sq. dm. for 10 minutes. The tin-nickel deposit was hazy-bright overthe entire panel.

EXAMPLE 14 The compound 1,S-diphenylcarbohydrazide in the amount of 0.10g./l. was added to the standard tin-nickel formulation in a Hull Cell. Asmooth brass panel was plated at an average current density of 2.7 amp./sq. dm. for 10 minutes. The tin-nickel deposit was hazy-bright over theentire panel.

EXAMPLE 15 The compound, phosphoric acid (H PO in the amount of 11 g./l.was added to the standard tin-nickel formulation in a Hull Cell. Asmooth brass panel was plated at an average current density of 2.7 amp./sq. dm. for 10 minutes. The tin-nickel deposit was clear-bright over thearea of the panel below about 3 amp/sq. dm. and hazy-bright on areasabove about 3 amp/sq. dm.

EXAMPLE 16 The compound, phosphoric acid (H PO in the amount of 6 g./l.was added to the standard tin-nickel formulation ina Hull Cell. A smoothbrass panel was plated at an average current density of 2.7 amp/sq. dm.for 10 minutes. The tin-nickel deposit was hazy-bright over the entirepanel.

EXAMPLE 17 The compound, phosphoric acid (H PO in the amount of 0.6g./l. was added to the standard tin-nickel formulation in a Hull Cell. Asmooth brass panel was plated at an average current density of 2.7 amp./sq. dm. for 1-0 minutes. The tin-nickel deposit was hazy-bright over theentire panel.

EXAMPLE 18 A combination of phenylpropiolic acid, 0.08 g./l., andstearamidopropyldimethyl (fl-hydroxyethyDammonium hydrogen phosphate,0.003 g./l., was added to the standard tin-nickel formulation in a HullCell. A smooth brass panel was plated at an average current density of2.7 amp./ sq. dm. for 10 minutes. The tin-nickel deposit wasclear-bright over the entire panel.

EXAMPLE 19 A combination ofstearamidopropyldimethyl-(ti-hydroxyethyl)ammonium dihydrogen phosphate,0.12 g./l. and phosphoric acid, 1.8 g./l. was added to the standardtin-nickel formulation in a Hull Cell. A smooth brass panel was platedat an average current density of 2.7 amp/sq. dm. for 10 minutes. Thetin-nickel deposit was clear-bright over the entire panel.

EXAMPLE 20 A combination of phenylpropiolic acid, 0.04 g./l. andphosphoric acid, 0.6 g./l., was added to the standard tinnickelformulation in a Hull Cell. A smooth brass panel was plated at anaverage current density of 2.7 amp/sq. dm. for 10 minutes. Thetin-nickel deposit was clearbright over the entire panel.

EXAMPLE 21 A combination of phenylpropiolic amide, 0.06 g./l. andphosphoric acid, 1 g./l., was added to the standard tinnickelformulation in a Hull Cell. A smooth brass panel was plated at anaverage current density of 2.7 amp/sq. dm. for 10 minutes. Thetin-nickel deposit was clearbright over the entire panel.

EXAMPLE 22 A combination of triaminotriphenyl methane, 0.02 g./l., andphosphoric acid, 0.5 g./l., was added to the standard tin-nickelformulation in a Hull Cell. A smooth brass panel was plated at anaverage current density of 2.7 amp./ sq. dm. for 10 minutes. Thetin-nickel deposit was clear-bright over the entire panel.

EXAMPLE 23 A combination of l-(p-aminophenyl)-3-methy1pyrazole, 0.1g./l., and phosphoric acid, 0.8 g./l., Was added to the standardtin-nickel formulation in a Hull Cell. A smooth brass panel was platedat an average current density of 2.7 an1p./ sq. dm. for 10 minutes. Thetin-nickel deposit was clear-bright over the entire panel.

EXAMPLE 24 A combination of 1,S-diphenylcarbohydrazide, 0.1 g./l., andphosphoric acid, 2.0 g./l. was added to the standard tin-nickelformulation in a Hull Cell. A smooth brass panel was plated at anaverage current density of 2.7 amp/sq. dm. for 10 minutes. Thetin-nickel deposit was hazy-bright over the entire panel.

Similar lustrous and bright deposits are obtained using the notedadditives with other acid baths, such as Bath 1 of Table II and theall-chloride bath formulation, at pH values below 1. The tin-nickelelectrodeposits obtained from the bright baths were strongly oriented inthe 300 plane. Utilizing these bright baths, it is possible toelectrodeposit bright tin-nickel directly on most basis metals includingsteel, copper and copper alloys, tin, nickel and nickel alloys, etc.Conventional cleaning of the basis metal prior to electrodepositionshould be practiced. The use of a bronze or copper undercoat on somebasis metals, particularly those electrochemically active in acid baths,is preferred.

As many embodiments of this invention may be made without departing fromthe spirit and scope thereof, it is to be understood that the inventionincludes all such modifications and variations as come within the scopeof the appended claims.

We claim:

1. An acidic aqueous electrolyte for bright tin-nickel platingcontaining Sn++ ions, Ni++ ions and an effective amount of at least onebrightener selected from the class consisting of phenylpropiolic acid,phenylpropiolic amide, triaminotriphenyl methane,1-(p-aminophenyl)-3-methylpyrazole,stearamidopropyldimethyl-(p-hydroxyethyl)ammonium dihydrogen phosphate,1,5-diphenylcarbohydrazide and phosphoric acid, to cause the tin-nickelelectrodeposit to be lustrous and bright.

2. An acidic aqueous electrolyte for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni ions and as a brightener, between0.01 g./l. and 0.3 g./l. of phenylpropiolic acid.

3. An acidic aqueous electrolyte for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni++ ions and as a brightener, between:05 g./l. and 0.2 g./l. of phenylpropiolic acid.

4. An acidic aqueous electroyte for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni++ ions and as a brightener, between0.01 g./l. and 0.3 g./l. of phenylpropiolic amide.

5. An acidic aqueous electrolyte for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni++ ions and as a brightener, between0.05 and 0.2 g./l. of phenylpropiolic amide.

6. An acidic aqueous electrolyte for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni++ ions and as a brightener between0.01 g./l. and 0.3 g./l. of triaminotriphenyl methane.

7. An acidic aqueous electrolyte for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni++ ions and as a brightener between0.05 g./l. and 0.2 g./l. of triaminotriphenyl methane.

8. An acidic aqueous electrolyte for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni++ ions and as a brightener between0.05 g./l. and 1 g./l. of l-(paminophenyl) -3-methy1pyrazole.

9. An acidic aqueous electrolyte for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni++ ions and as a brightener between0.2 g./1. and 0.5 g./l. of l-(paminophenyl)-3-methylpyrazole.

10. An acidic aqueous electrolyte for the electrodeposition of brighttin-nickel containing Sn ions, Ni++ ions and as a brightener between0.001 g./l. and 0.2 g./l. of stearamidopropyldimethyl (5hydroxyethyl)ammoniurn dihydrogen phosphate.

11. An acidic aqueous electrolyte for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni++ ions and as a brightener between0.01 g./1. and 0.1 g./l. of stearamidopropyldimethyl (BhydroXyethyDammonium dihydrogen phosphate.

12. An acidic aqueous electrolyte for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni++ ions and as a brightener between0.05 g./l. and 0.5 g./l. of l,5-diphenylcarbohydrazide.

13. An acidic aqueous electrolyte for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni ions and as a brightener between 0.2g./l. and 0.3 g./l. of 1,5- diphenylcarbohydrazide.

14. An acidic aqueous electrolyte for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni++ ions and as a brightener between0.1 g./l. and 15 g./l. of phosphoric acid.

15. An acidic aqueous electrolyte for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni++ ions and as a brightener between0.5 g./l. and 7 g./l. of phosphoric acid.

16. An acidic aqueous bath for the electrodeposition of brighttin-nickel containing Sn++ ions, Ni++ ions and between 0.0005 g./l. and0.5 g./l. of stearamidopropyldimethyl (,6 hydroxyethyhammoniumdihydrogen phosphate, and between 0.007 g./l. and 0.7 g./l. ofphosphoric acid.

17. A composition of matter capable of brightening activity whenincorporated in an acidic tin-nickel electroplating bath, saidcomposition containing water and 5 g./l. to 200 g./l. of phosphoric acidand 5 g./l. to 50 g./l. of at least one compound selected from the classconsisting of phenylpropiolic acid, phenylpropiolic amide,triaminotriphenyl methane, l-(p-aminophenyl)-3-methylpyrazole,stearamidopropyldimethyl (B hydroxyethyl)- ammonium dihydrogenphosphate, and 1,5-diphenylcarbohydrazide.

18. In the process for electrodepositing bright tin-nickel from anaqueous fluoride-chloride tin-nickel electrolyte, the improvementcomprising adding to said electrolyte an amount of at least onebrightener selected from the class consisting of phenylpropiolic acid,phenylpropiolic amide, triaminotriphenyl methane,l-(p-aminophenyl)-3-methylpyrazole, stearamidopropyldimethyl (,8hydroxyethyD- ammonium dihydrogen phosphate, 1,5-diphenylcarbohydrazideand phosphoric acid, sufficient to cause the tinnickel electrodeposit tobe lustrous and bright.

19. A chlorine and fluorine containing acidic bath for tin-nickelelectroplating having a pH between about 2 and 2.5, and containingbetween 26 g./l. and 37.5 g./l. of Sn++ ions, between 60 g./l. and 82.5g./l. of Ni++ ions, between 34 g./1. and 45 g./l. of F ions, andcontaining an effective amount of at least one brightener selected fromthe class consisting of phenylpropiolic acid, phenylpropiolic amide,triaminotriphenyl methane l-(p-aminophenyl) 3 methylpyrazole,stearamidopropyldimethyl (flhydroxyethyhammonium dihydrogen phosphate,1,5-diphenylcarbohydrazide and phosphoric acid, to cause the tin-nickelelectrodeposit to be lustrous and bright.

20. The bath of claim 19 containing about 49 g./l. of stannous chloride,about 300 g./l. of hydrated nickel chloride, about 56 g./l. of ammoniumbifluoride, and sufficient ammonium hydroxide to adjust the pH tobetween 2 and 2.5.

21. A chlorine and fluorine containing acidic bath for tin-nickelelectroplating having a pH between about 2 and 2.5, and containingbetween 26 g./l. and 37.5 g./l. of Sn++ ions, between 60 g./l. and 82.5g./1. of Ni++ ions, between 34 g./l. and 45 g./l. of F ions, andcontaining between 0.01 g./l. and 0.3 g./l. of phenylpropiolic acid.

22. The bath of claim 21 containing about 49 g./l. of stannous chloride,about 300 g./l. of hydrated nickel chloride, about 5 6 g./l. of ammoniumbifiuoride, and sufficient ammonium hydroxide to adjust the pH tobetween 2 and 2.5.

2,646,397 Wean July 21, 1953 10 Parkinson Nov. 10, 1953 Ford et al Aug.19, 1958 Taylor et a1. Feb. 23, 1960 Meyering Mar. 7, 1961 Boggs June20, 1961 Seyb Oct. 3, 1961 FOREIGN PATENTS Great Britain Nov. 18, 1915France Mar. 11. 1957

1. AN ACIDIC AQUEOUS ELECTROLYTE FOR BRIGHT TIN-NICKEL PLATINGCONTAINING SN++ IONS, NI++ IONS AND AN EFFECTIVE AMOUNT OF AT LEAST ONEBRIGHTENER SELECTED FROM THE CLASS CONSISTING OF PHENYLPROPIOLIC ACID,PHENYLPROPIOLIC AMIDE, TRIAMINOTRIPHENYL METHANE,1-(P-AMINOPHENYL)-3-METHYLPYRAZOLE,STEARAMIDOPROPYLDIMETHYL-(B-HYDROXYETHYL)AMMONIUM DIHYDROGEN PHOSPHATE,1,5-DIPHENYLCARBOHYDRAZIDE AND PHOSPHORIC ACID, TO CAUSE THE TIN-NICKELELECTRODEPOSIT TO BE LUSTROUS AND BRIGHT.